diff options
| author | Jens Axboe <axboe@kernel.dk> | 2017-06-20 17:56:13 -0600 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2017-06-21 10:17:49 -0600 |
| commit | 8e8320c9315c47a6a090188720ccff32a6a6ba18 (patch) | |
| tree | e407c7eb7afd9d09aea9355426a2942a295be946 /include | |
| parent | ec2f0fadde446e0ebe28c779ffcac655228b8f1e (diff) | |
blk-mq: fix performance regression with shared tags
If we have shared tags enabled, then every IO completion will trigger
a full loop of every queue belonging to a tag set, and every hardware
queue for each of those queues, even if nothing needs to be done.
This causes a massive performance regression if you have a lot of
shared devices.
Instead of doing this huge full scan on every IO, add an atomic
counter to the main queue that tracks how many hardware queues have
been marked as needing a restart. With that, we can avoid looking for
restartable queues, if we don't have to.
Max reports that this restores performance. Before this patch, 4K
IOPS was limited to 22-23K IOPS. With the patch, we are running at
950-970K IOPS.
Fixes: 6d8c6c0f97ad ("blk-mq: Restart a single queue if tag sets are shared")
Reported-by: Max Gurtovoy <maxg@mellanox.com>
Tested-by: Max Gurtovoy <maxg@mellanox.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Tested-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/blkdev.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index b74a3edcb3da..1ddd36bd2173 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -391,6 +391,8 @@ struct request_queue { int nr_rqs[2]; /* # allocated [a]sync rqs */ int nr_rqs_elvpriv; /* # allocated rqs w/ elvpriv */ + atomic_t shared_hctx_restart; + struct blk_queue_stats *stats; struct rq_wb *rq_wb; |